The present invention relates to implantable devices (or implants) of active type.
This term xe2x80x9cimplantsxe2x80x9d is intended to indicate devices intended to be implanted in the body of a patient and the function of which is not limited to the replacement or functional assistance of an organ or a part of an organ of the human body (which may be the case, for example, with a cardiac valve prosthesis or so-called vascular graft). On the contrary, an active implantable device is generally able to recognise the occurrence of a particular physiological picture and then give a specific reaction.
Cardiostimulators (currently known as pacemakers) are a typical example of active implantable devices: these latter are in general able to recognise the absence or insufficiency of the natural cardiac stimulation and to respond in such a way as to replace this missing or insufficient stimulation with a stimulation produced by the device itself, acting as a function of the activity of the patient (so-called xe2x80x9crate responsivexe2x80x9d stimulators).
It is also known that implant devices such as cardiostimulators as mentioned above, can be provided with a so-called telemetry function which, as well as allowing programming of the stimulator from a distance (and therefore in an extracorporeal manner), also makes it possible to emit, for example to a monitoring station supervised by an operator, signals indicative of the conditions of the wearer.
Also known in the art are so-called xe2x80x9cdrug dispenserxe2x80x9d implants which are able to achieve a targeted delivery of a predetermined drug, also in dependence on a signal indicative of the establishment of particular conditions in the body of the patient.
The present invention, which has been developed with a view to preferential (although not exclusive) application to the treatment of cardiac conditions, is based on the recognition of several essential facts:
almost all active implants available up to now are only able to treat cardiac conditions of the xe2x80x9celectricalxe2x80x9d type, such as for example insufficient stimulation;
some electrical cardiac conditions (such as for example, atrial fibrillation) are not treatable in a satisfactory manner with only electrical stimulation, whilst, on the other hand, important results in the treatment of such conditions have been obtained with a pharmaceutical treatment; and
important cardiac conditions (such as the so-called congestive heart failure, currently called CHF) are difficult to monitor, expensive to treat and often have unfavourable consequences if not monitored and treated in a timely manner.
By examining more closely the two above-considered conditions (which it is intended should not exhaust the range of possible applications of the invention) the following can be observed.
Atrial fibrillation is essentially a form of cardiac arrhythmia characterised by rapid and irregular atrial electrical impulses and by inefficient atrial contractions. The atrial rhythm can be up to 400-650 beats per minute, whilst the ventricular rhythm varies in an irregular manner between 100 and 180 beats per minute. Atrial fibrillation can have a paroxysmic origin at different points of the sinoatrial node and is typically multifocal. It may terminate spontaneously in an unexpected manner, but often becomes chronic.
The consequences lead substantially to a loss of effectiveness of the atrial contraction (the so-called xe2x80x9catrial kickxe2x80x9d) and to a loss of the correct management of the cardiac frequency according to metabolic requirements (so-called chronotropic incompetence), and to the frequent manifestation of arrhythmias with an irregular and rapid ventricular rhythm. All this leads to a general reduction of efficiency in the pumping action of the cardiac muscle (unbalanced, low resistance to forces), to an increase in the formation of intracardiac thromboses (with consequent risk of cerebral ictus), to ventricular tachycardia, and, in general, to a reduced quality of life with increasing risk of mortality.
The main methods of treatment currently known range from surgical treatment (which is traumatic and certainly not suitable in all cases) to external electric defibrillation (which at times is not effective and may not be in time) to ablation of the ectopic sites at the base of the arrhythmias (a technique which must, however, remain of an experimental nature), to pharmacological treatment. This latter type of treatment, which is of an anti-rhythmic nature, is essentially directed at reducing the recurrence of fibrillation (by administration of quinidine, flecainide, propafenone, sotalol or disopyramide), reducing the cardiac frequency (by the administration of digitalis products and b-blockers) or has an anti-coagulant function to reduce the risk of ictus and other thromboembolic events (administration of aspirin, warfarin), and is certainly promising, but is not conclusive in that it is not free from contra-indications or risks.
It is possible therefore to assert that in order to be certainly effective of treatment must to some extent be able to count at least in principle, on at least some of the forms of treatment described above, performed in a co-ordinated framework of concurrent actions of diverse nature.
This is also substantially true for congestive heart failure (CHF). This latter essentially leads to a weakening and then a reduced function of the cardiac muscle as a pumping member, and is in particular able to cause significant difficulty in filling and/or emptying of the left ventricle and therefore an insufficient cardiac capacity.
The main consequences are dispnea and a greater sense of fatigue from effort, ventricular arrhythmia (and in particular atrial fibrillation), an increase in sympathetic tone with a reduction of parasympathetic tone, thromboembolisms, retention of fluids and an increased risk of myocardiac infarction. All this with a significant increase in the mortality rate in particular by unexpected death and by terminal cardiac insufficiency.
The current methods of treatment are pharmacological, with the administration of digitalis products, diuretics or vasodilators. Such treatment, which is not always effective and the therapeutic effect of which is not demonstrated, can be the herald of collateral effects.
Electrical stimulation has also been practised, which however is of limited effectiveness and is only usable in a small category of patients, the same considerations applying to the technique of cardiomyoplasty.
A greater effectiveness, at least in some cases and on a temporary basis, can be achieved by recourse to ventricular assistance devices (VAD) or to artificial hearts. This, however, involves, as is well known, arrangements which are usable for only a limited time, and are such as to require intensive hospital assistance (with consequent high treatment costs), involving intrinsically more difficult techniques allied to the fact that ventricular assistance devices usually require, for their operation, service supply means (electrical energy, fluid under pressure etc.) from sources located outside the body of the patient, via supply lines of a transcutaneous nature.
A limited solution is represented by (total or partial) transplant of the cardiac muscle, a solution which however comes up against limited availability of donors, problems of biocompatability, high initial and follow up costs and risks of possible degeneration.
The experience of treating these conditions demonstrates that very often the possibility of achieving an effective treatment, whatever its type, depends critically on the possibility of monitoring the patient""s condition and/or signalling in a timely manner to the outside (to the patient himself and/or to an assistance centre to which he can go) the establishment of or, better still, the probable approach of a crisis state. In this way it is possible, for example, to cause the patient to interrupt an activity which may be critical because of the conditions and/or to go straight to an assistance centre, or even cause the assistance centre, alerted in an automatic manner, to locate the patient, leading it to him, to then subject him to the specific treatments such as those which can be performed, for example, in an intensive care unit of a hospital.
The present invention seeks to provide an active implant device able to respond in an optimal manner to the detection and treatment requirements described above. According to the present invention, this object is achieved by an implant device having the characteristics specifically set out in the claims.
This invention is an active implantable device comprising a sensor means capable of detecting signals indicative of the conditions of the wearer of the device; a processor means capable of selectively identifying, from signals detected by the sensor means, particular conditions of the wearer of the device such as to require the intervention of assistance; an actuator means capable of inducing the performance of therapeutic actions on the body of the wearer upon the occurrence of the particular conditions of the wearer of the device; and a telemetry means capable of signalling out from the body of the wearer of the device the occurrence of the particular conditions of the wearer of the device. The sensor means may include an interface unit capable of transferring to the processor means the signals detected by at least one sensor element implanted in the body of the patient. Preferably, the sensor means is sensitive to one of the following: electrocardiograph signals (ECG) of the wearer of the device; the signal relating to the natural heart acceleration (NHA) of the wearer of the device, and the blood pressure (BP) of the wearer of the device.
The device may also comprise at least one interface for converting respective control signals generated by the processor means into respective activation signals for at least one of the actuator means for performing a therapeutic action on the body of the wearer of the device.
Preferably, the actuator means is capable of inducing at least one of the following therapeutic actions on the body of the wearer of the device: an electrical stimulation action, and a drug infusion.
The telemetry means may comprise a short distance telemetry section for the transmission, from the body of the wearer of the device, of monitoring signals identifying the particular conditions of the wearer of the device identified by the processor means from signals detected by the sensor means.
Alternatively, the telemetry means may include a long distance telemetry section for the transmission, from the body of the wearer of the device, of at least one warning signal identifying the occurrence of the particular conditions of the wearer of the device identified by the processor means from the signals detected by the sensor means.
The telemetry means may have at least one of the following associated units: a telecommunications unit for sending warning and/or data signals to a telecommunications network, and a position location unit for locating the whereabouts of the wearer of the device . The telecommunications unit may be in the form of a mobile radio unit.
The position locating unit preferably is a position locating unit of a telecommunications network. The position locating unit is capable of sending the associated position locating signal of the wearer of the device to the telecommunications unit for forwarding a corresponding message for locating the position of the wearer of the device.